Why genetic counseling is sometimes important before and during pregnancy

The main reasons why a woman seeks genetic counseling prior to or during her pregnancy mainly fall in the following groups:

Ethnic predispositions to inherited disorders
Family history of a baby with genetic disorders.
History of babies born with birth defects
Advanced maternal age.
Abnormal test results in pregnancy.
Exposure to potentially harmful substances or, organisms during pregnancy.

Let us consider each aspect one by one


Significance of Ethnic origin of parents

Ethnic predilection to a genetic disorder is definite necessity to undergo genetic testing and counseling during pregnancy, and even better if before. The following diseases are a autosomal recessive. They need two genes—one from each otherwise healthy parent—for the condition to manifest in a child.

The following diseases are few of the conditions transmitted in this way:

Sickle Cell disease.

In sickle cell disease, the usually supple and round red blood cells become stiff and crescent-shaped. This condition causes anemia, bouts of pain caused by obstructed blood vessels, and enhanced vulnerability to serious infections like pneumonia. About 1 out of 10 African-Americans carries one recessive gene for sickle cell disease. This condition is called sickle cell trait. More than 50,000 Americans have both the copies of the gene in them and have sickle cell disease. When both parents have sickle cell trait, they have a one in four probability with each pregnancy of having a child with the sickle cell disease. This can be diagnosed during pregnancy by prenatal screening or, at birth by carrying on investigation on the new born.

Thalassemia.

Those of Asian and Mediterranean origin including Greeks and Italians are at threat of inheriting thalassemia when both partners carry a single recessive gene also known as thalassemia trait. Some forms of thalassemia like Majors are very grave and may end in stillbirth or cause severe anemia, needing a continuous blood transfusions for the child or sometimes bone marrow transplantation may be required. Prenatal screening is possible for thalassemia.

Tay-Sachs disease.

Those from Eastern European (Ashkenazi) Jewish descent might be carriers of the recessive genes for a number of disorders, of which Tay-Sachs disease is very important. Babies with Tay-Sachs disease are deficient in an enzyme, hexosaminidase A from birth. This is essential for nerve cell to function properly. These children steadily deteriorate their mental and physical function and usually expire before they reach their fifth birthday. Approximately 1 out of 25 Ashkenazi Jews is a Tay-Sachs carrier. The ratio for Sephardic Jews (those originally from Spain, Portugal, and North Africa) is about 1 out of 100. Screening with a simple blood test during or before pregnancy is a routine practice, and prenatal testing is possible.

Gaucher disease

Another recessive genetic disease characterized by an enzyme deficiency is Gaucher disease. It is commoner than Tay-Sachs disease, with a gene carrier ratio of approximately 1 out of 12 Ashkenazi Jews.

In Gaucher disease there is building up of fatty deposits in the liver and spleen. This results in the enlargement of these organs. It can range from mild to severe. Carrier screening and prenatal diagnosis are possible to those with a family history of the condition.

Cystic fibrosis.

Caucasians are at a bigger risk for cystic fibrosis (CF), in general a severe disease condition characterized by thick and sticky mucus secretions mainly in the lungs and other parts of the body. There are roughly 30,000 Americans with Cystic Fibrosis and as many as 1 Caucasian American out of 20 may carry one of the many types of the gene for Cystic Fibrosis.

Cystic Fibrosis is infrequent in Latinos, African-Americans, and very unusual among the Asians. When both the partners of a couple carry such a gene, they have a one in four probability with each pregnancy of giving birth to a child with Cystic Fibrosis.

Currently, a DNA-based investigation for the cystic fibrosis gene is existing, particularly to couple with a family history of Cystic Fibrosis. In the majority of instances, a fetus at risk for Cystic Fibrosis with a family history can be recognized through prenatal screening.

The diseases mentioned above are only the tip of the icebarg of the numerous genetic disorders for which specific ethnic groups are particularly at risk.